package org.tgit.gateway.common;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class MDY {

	 private static final String HEX_NUMS_STR="0123456789ABCDEF";
	 private static final Integer SALT_LENGTH = 12;
	  
	 /** 
	 * 将16进制字符串转换成字节数组 
	 * @param hex 
	 * @return 
	 */
	 public static byte[] hexStringToByte(String hex) {
		 int len = (hex.length() / 2);
		 byte[] result = new byte[len];
		 char[] hexChars = hex.toCharArray();
		 for (int i = 0; i < len; i++) {
			 int pos = i * 2;
			 result[i] = (byte) (HEX_NUMS_STR.indexOf(hexChars[pos]) << 4
			 | HEX_NUMS_STR.indexOf(hexChars[pos + 1]));
		 }
		 return result;
	 }
	 
	  
	 /**
	 * 将指定byte数组转换成16进制字符串
	 * @param b
	 * @return
	 */
	 public static String byteToHexString(byte[] b) {
		 StringBuffer hexString = new StringBuffer();
		 for (int i = 0; i < b.length; i++) {
			 String hex = Integer.toHexString(b[i] & 0xFF);
			 if (hex.length() == 1) {
			 hex = '0' + hex;
		 }
			 hexString.append(hex.toUpperCase());
		 }
		 return hexString.toString();
	 }
	  
	 /**
	 * 验证口令是否合法
	 * @param password
	 * @param passwordInDb
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws UnsupportedEncodingException
	 */
	 public static boolean validPassword(String password, String passwordInDb) throws NoSuchAlgorithmException, UnsupportedEncodingException {
		 //将16进制字符串格式口令转换成字节数组
		 byte[] pwdInDb = hexStringToByte(passwordInDb);
		 //声明盐变量
		 byte[] salt = new byte[SALT_LENGTH];
		 //将盐从数据库中保存的口令字节数组中提取出来
		 System.arraycopy(pwdInDb, 0, salt, 0, SALT_LENGTH);
		 //创建消息摘要对象
		 MessageDigest md = MessageDigest.getInstance("MD5");
		 //将盐数据传入消息摘要对象
		 md.update(salt);
		 //将口令的数据传给消息摘要对象
		 md.update(password.getBytes("UTF-8"));
		 //生成输入口令的消息摘要
		 byte[] digest = md.digest();
		 //声明一个保存数据库中口令消息摘要的变量
		 byte[] digestInDb = new byte[pwdInDb.length - SALT_LENGTH];
		 //取得数据库中口令的消息摘要
		 System.arraycopy(pwdInDb, SALT_LENGTH, digestInDb, 0, digestInDb.length);
		 //比较根据输入口令生成的消息摘要和数据库中消息摘要是否相同
		 if (Arrays.equals(digest, digestInDb)) {
			 //口令正确返回口令匹配消息
			 return true;
		 } else {
			 //口令不正确返回口令不匹配消息
			 return false;
		 }
	 }
	 
	 
	 /**
	 * 获得加密后的16进制形式口令
	 * @param password
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws UnsupportedEncodingException
	 */
	 public static String getEncryptedPwd(String password) throws NoSuchAlgorithmException, UnsupportedEncodingException {
		 //声明加密后的口令数组变量
		 byte[] pwd = null;
		 //随机数生成器
		 SecureRandom random = new SecureRandom();
		 //声明盐数组变量
		 byte[] salt = new byte[SALT_LENGTH];
		 //将随机数放入盐变量中
		 random.nextBytes(salt);
		 //声明消息摘要对象
		 MessageDigest md = null;
		 //创建消息摘要
		 md = MessageDigest.getInstance("MD5");
		 //将盐数据传入消息摘要对象
		 md.update(salt);
		 //将口令的数据传给消息摘要对象
		 md.update(password.getBytes("UTF-8"));
		 //获得消息摘要的字节数组
		 byte[] digest = md.digest();
		 //因为要在口令的字节数组中存放盐，所以加上盐的字节长度
		 pwd = new byte[digest.length + SALT_LENGTH];
		 //将盐的字节拷贝到生成的加密口令字节数组的前12个字节，以便在验证口令时取出盐
		 System.arraycopy(salt, 0, pwd, 0, SALT_LENGTH);
		 //将消息摘要拷贝到加密口令字节数组从第13个字节开始的字节
		 System.arraycopy(digest, 0, pwd, SALT_LENGTH, digest.length);
		 //将字节数组格式加密后的口令转化为16进制字符串格式的口令
		 return byteToHexString(pwd);
	 }
	 private static Map users = new HashMap();
	  
	 public static void main(String[] args){
		 String userName = "zyg";
		 String password = "123";
		 registerUser(userName,password);
		  
		 userName = "changong";
		 password = "456";
		 registerUser(userName,password);
		  
		 String loginUserId = "zyg";
		 String pwd = "1232";
		 try {
		 if(loginValid(loginUserId,pwd)){
			 System.out.println("欢迎登陆！！！");
		 }else{
			 System.out.println("口令错误，请重新输入！！！");
		 }
		 } catch (NoSuchAlgorithmException e) {
		 // TODO Auto-generated catch block
		 e.printStackTrace();
		 } catch (UnsupportedEncodingException e) {
		 // TODO Auto-generated catch block
		 e.printStackTrace();
		 } 
	 }
	  
	 /**
	 * 注册用户
	 * 
	 * @param userName
	 * @param password
	 */
	 public static void registerUser(String userName,String password){
		 String encryptedPwd = null;
		 try {
			 encryptedPwd = getEncryptedPwd(password);
			  
			 users.put(userName, encryptedPwd);
		  
		 } catch (NoSuchAlgorithmException e) {
		 // TODO Auto-generated catch block
		 e.printStackTrace();
		 } catch (UnsupportedEncodingException e) {
		 // TODO Auto-generated catch block
		 e.printStackTrace();
	 }
	 }
	  
	 /**
	 * 验证登陆
	 * 
	 * @param userName
	 * @param password
	 * @return
	 * @throws UnsupportedEncodingException 
	 * @throws NoSuchAlgorithmException 
	 */
	 public static boolean loginValid(String userName,String password) 
		 throws NoSuchAlgorithmException, UnsupportedEncodingException{
		 String pwdInDb = (String)users.get(userName);
		 if(null!=pwdInDb){ // 该用户存在
			 return validPassword(password, pwdInDb);
		 }else{
		 System.out.println("不存在该用户！！！");
		 	return false;
		 }
	 }

}
